John 15:27

καὶ ὑμεῖς δὲ μαρτυρεῖτε, “and do ye also witness,” or, if indicative, “and ye also witness”. Most prefer the indicative. “The disciples were already the witnesses which they were to be in the future.” Meyer. This agrees with the ἐστε following. They were able to act as witnesses ὅτι ἀπʼ ἀρχῆς μετʼ ἐμοῦ ἐστε, “because from the beginning,” of the Messianic activity, “ye are with me”. The present, ἐστε, is natural as Jesus is looking at their entire fellowship with Him, and that was still continuing. Cf. Mark 3:14, ἐποίησε δώδεκα, ἵνα ὦσι μετʼ αὐτοῦ; also Acts 1:21; Acts 4:13.